Gun sight



5 H. IRASEK Nov. 27, 1951 GUN SIGHT 6 Sheets-Sheet 1 led June 2, 1945 I m F V INVENTOR EGENE H. IRASEK BY I fl ATTORNEY 5;

gamma": KUUW Nov. 27, 1951 E. H. IRASEK 2,576,120

GUN SIGHT Filed June 2, 1945 e Sheets-Sheet 2 "MAW INVENTOR EUGENE H. mass/r ATTORNEY E. H. IRASEK Nov. 27, 1951 GUN SIGHT 6 Sheets-Sheet 3 Filed June 2, 1945 INVENTOR EUGENE H. muss/r Xfi ATTORNEY Nov. 27, 1951 E. H. IRASEK 7 GUN SIGHT Filed June 2, 1945 v v 6 Sheets-Sheet 4 FIG. l0 l0 INVENTOR EUGENE H. IRASEK X3. dfi f ATTORNEY Nov. 27, 195

E. H. IRASEK GUN SIGHT 6 Sheets-Sheet 5 Filed June 2, 1945 direction of Axis of Bore FIG. 13

' INVENTOR EUGENE H. IRASEK 'ATTORNEY mm Win2 Nov. 27, 1951 E. H. IRASEK GUN SIGHT 6 Sheets-Sheet 6 82 FIG. 15

Filed June 2, 1945 ATTORNEY I m H n 1 v \xw V INVENTOR EUGbl/f H. IRASEK BY Patented Nov. 27, 1951 t. l thrill; t k; l i

UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

The present invention relates to fire control apparatus, and particularly to improvements in compensating sighting devices. While disclosed in connection with a gunsight installed in an airplane, it will be recognized that the invention is equally applicable to related or analogous items of ordnance such as rocket projectors and the like. The word gun as used in the specification and claims is accordingly intended to include all other dirigible projecting devices for ordnance projectiles.

An important object of the invention is to provide a compensating sight of small and compact construction, adapted to be mounted directly upon a gun of the freely movable type, such, for example, as a pedestal-supported or turret mounted machine gun, and which is particularly suitable for installation upon rapidly moving vehicles, such as aircraft; functioning, when utilized in the aiming of a gun, to compensate for the speed of the aircraft itself by deflecting the line of sight automatically, continuously and in proportion to the speed of the aircraft upon which the gun and sight are mounted. More precisely stated, the sighting device provides continuous and instantaneous correction for the component of own ships speed transverse to the axis of the gun bore.

Another important object of the invention is to provide such a compensating sight which provides a vector solution of the angle representing the total desired deflection of the axis of the gun bore with respect to the line of sight. The sighting mechanism, which will be explained in connection with an airplane installation, continually adjusts the deflection angle in a manner which continuously takes into account the angle be tween the line of flight and the axis of the gun bore and which presents its solution regardless of the relative attitudes of the gun-carrying airplane and its target.

An object related to that last stated is to provide such an automatic compensating sight mechanism consisting basically of vector linkage having one bar connected to and adapted to control the deflection of the sighting device, movement of an end of said bar remote from the sighting device being controllable, through the agency of an improved gearing arrangement of simple and accurate character, to effect both lateral and vertical deflection of the sight.

Still another object is to provide such a mechanism wherein the gearing previously mentioned permits movement of said end of the bar to any desired position upon the surface of a sphere, the mechanism being so designed that such movements are uniformly proportional to the movements of the gun in train and elevation and in a direction to maintain a fixed relationship between said end of the bar and the axis of flight of the airplane.

Another object is to provide such a sighting mechanism incorporating a vector linkage having a main bar controllable in the manner previously indicated and incorporating permanently accurate, simple and rugged means for changing the effective length of said bar, whereby the ratio between its angular deflection and the deflection of the gun in elevation and trainis varied to compensate for variances in the speed of the aircraft.

Other objects and advantages will be apparent from a consideration of the present disclosure in its entirety.

, mount, illustrating an improved gunsight constructed in accordance with the present invention installed upon the gun;

Figure 2 is a fragmentary perspective view of a portion of the mount, showing the gearing for driving the sight mechanism in response to training movements of the gun;

Figure 3 is a detailed perspective view of a portion of the means for driving the sight mechanism in response to elevational movements of the gun;

Figure 4 is a perspective view of the principal components of my improved sight, the casing and other portions being broken away for clarity of illustration;

Figure 5 is a similar perspective view, partly broken away, showing the rear portion of the sight and. showing the manner of locking the sighting mechanism in centered position for bore sighting;

Figure 6 is a sectional detail taken substantially on the line 66 of Figure 4 and looking in the direction of the arrows;

Figure 7 is a central vertical sectional view of my improved sight;

Figure 8 is a horizontal sectional plan view thereof;

Figures 9 and 10 are vertical sectional views taken substantially on the lines 9 -9 and Ill-H) respectively of Figure 8 and looking in the direction of the arrows;

Figure 11 is a vertical sectional view taken substantially on the line Illl of Figure 1 and looking in the direction of the arrows;

Figure 12 is a diagrammatic view, illustrating the problem and solution involved under the con-' ditions obtaining when the gun is trained perpendicularly with respect to the line of flight;

Figure 13 is a view partly in perspective and partly in diagrammatic form, the diagram also being in perspective and indicating the slant plane in which the true solution lies under the more usual conditions obtaining when the axis of the gun lies along a line neither coinciding with nor perpendicular to the line of flight;

Figure 14 is a vertical longitudinal section of a modified illuminated sighting device.

Figure 15 is a view partly in elevation and partly in transverse section of the sighting device of Figure 14;

Figure 16 is a top plan view of the same; and

Figure 17 is an exploded perspective view of the principal components of the same.

The lead-generating mechanism is contained in a compact housing I of rectangular form, adapted to be rigidly fastened to the gun in a convenient position directly above the breech. A pedestal 3 is provided which is adapted to be secured by screws I to the cover of the receiver of a machine gun, generally designated 5 and shown in Figure 1 as of the Browning type. The sight casing I is supported at its front end upon a cross shaft 2 mounted in a bracket 6 supported by and swingable about the axis of a vertical screw 1 carried by the forward end of pedestal 3. At its rear end the sight casing is connected to the pedestal by a vertical screw 8 extending downwardly from thecasing through an enlarged hole II in the pedestal. Two adjusting nuts I2 are threaded upon the screw 8 and have flanges I2 and I2 overlying and underlying the pedestal to permit vertical adjustment of the screw and of the angle of elevation of the sight body. This is particularly useful in connection with boresighting. At its upper end the screw 8 is fast in a tapped sleeve or traveler I3 threaded on a transverse screwshaft I I journaled but held against axial movement in the sidewalls of casing I. Friction material I9 in a well (undesignated) in one end of the traveler resists rotation of the screwshaft and takes up play between the screw threads and the traveler. The screwshaft is provided with a slotted head I 4' on one side of the casing. Rotation of this shaft swings the sight casing in azimuth about the axis of front supporting screw 1. The top vertical adjusting nut I2 may carry a dial l2 calibrated in yards or other suitable indicia to indicate the distance from the muzzle at which the trajectory may be expected to cross the transverse plane of the line of sight when the gun is horizontal and the angularity of the line of sight with respect to the gun axis is set by the dial.

A sighting device generally designated Ill projects upwardly from the casing I in a convenient position for sighting. The lead required to compensate for the speed of the plane upon which the gun and sight are mounted is generated by the mechanism within the casing I and functions to deflect the sight ID to such extent that when the target is centered in the sight, the gun axis leads the sight axis by the proper amount The correcting mechanism is driven by the training and pointing movements of the gun, and sight deflection occurs without delay in a smooth and continuous manner, although correction is provided only for the speed of the plane upon which the gun and sight are installed and not for target speed. It will be appreciated that the sight is therefore primarily adapted for use against ground targets, and against airplanes attacking the ship upon a pursuit course.

Since the required lead angle is dependent upon the component of own ships speed transverse to the line of fire of the gun, it will be apparent that sight deflection must be altered with and proportionately to elevational and training movements of the gun, assuming constant own ships speed. It will also be appreciated that if the gun is universally movable in its mount, the proper lead angle may lie in a plane inclined in any direction, so that the sighting means must also be universally movable with respect to the gun, although positively guided and controlled. In the embodiment of Figures 1-11 inclusive, the sight I0 is pivoted for independent vertical or elevational movement with respect to the gun in P trunnions provided by a supporting fork I 5, which is also transversely swingable independently in train about an axis provided by a post I6 journaled in vertically spaced bearings shown as of the ball type, and designated H, in a longitudinally slidable carriage 20 forming the top of the casing I. At its lower end the post I6 carries a fork I8 the downwardly projecting arms of which are articulated to a yoke 22 extending longitudinally within the casing I and constituting one of the elements of a system of parallel linkage by which mechanical movement is imparted to the sight. The upper horizontal elements of the linkage system are provided by integral arms 2I projecting rearwardly from the frame of the sight I0 and pivoted at their rear extremities to the upper end of the rear vertical link assembly, formed by the rod 24. At its lower end the rod 24 is pivoted to yoke 22 by means of the fork 26,. At its upper end the ring 21, also fast upon rod 24, provides connection to the arms 2I. The rod 24 projects through the free space behind the carriage 20 and is movable both laterally and vertically, coacting with post IE to maintain the sight parallel to the yoke 22. The yoke 22 is universally movable about a center. defined by the intersection of the downwardly extended axis of the post I6 and the trunnion axis of yoke I8.

Movement is imparted to the yoke 22 by a slide bar 30 of dovetailed cross-section which is longitudinally movable in a slideway 32 formed in the bottom of yoke 22. Slide bar 30 is rigidly attached to and forms an extension ofthe arm 33. In the linkage system the line of sight is repre sented by the ideal arm of which arm 33 is the physical embodiment. The link corresponding to the gun axis is furnished by the casing I itself, while the angular relationship between arm 33 and the gun axis, for a given air speed, is a vector resultant of the bullet velocity vector lying along the gun axis and a vectorv representative of the velocity of the airplane along the line of flight.

Although the forward portion of arm 33 is offset to provide clearance between the arm and the deflection gearing by which it is actuated, the ideal length of the arm extends through a ball joint by which such arm is coupled to the gearing.

. The ball element 35, rigidly attached to the forward extremity of the arm, is rotatably fitted within a ball socket 36 carried by a crank 38 rotatably mounted at a fixed radius from the rotational axis of a driven miter gear 40. The ball socket is provided with a threadedly adjustable take-up section 3'! (Fig. 6). Gear 40 is rotatably mounted in a carrier 4| which permits the gear, in addition to rotating upon its own axis, to revolve in a controlled orbit the plane of which is disposed centrally, vertically and longitudinally of the case I. The gear carrier III is formed with an integral hub 42 journaled in the side of the case in a bearing boss formed by an attached flange sleeve 43. The hub 42 is preferably mounted in antifriction bearings as 44, and an integral extension 45 of the hub projects from the sleeve 43 to permit attachment of a clamp 41 by which the hub and the attached carrier may be driven. Hub 42 and extension 45 are hollow, and a shaft -50 extends therethrough and is freely rotatable therein. A miter gear 39 fast upon the inner end of shaft 50 meshes with and serves to drive the gear 40 to rotate the latter about its own axis and so enable lateral displacement of the arm 33.

Rotation of the carrier 4|, except when the center of ball 35 lies upon the extended axis of shaft 50', displaces the arm 33 and so the sight element elevational movements of the gun. An arm 46 integral with clamp 41 is articulated as by means ofa link 48 to a fixed arm 48 rigidly attached to and projecting from one of the gun trunnions 48 Also integral with the clamp 41 is a bracket 49 supporting a worm 5| meshing with a worm wheel 52 fast upon the projecting end of shaft 50. Worm 5| is driven by training movements of the gun, through the agency of a flexible shaft 53 to which the worm is attached, the shaft being rotatable by a pinion 54 attached to its lower end and running upon a circular rack 55 attached to the pedestal 56 and concentric with the training axis.

It will be noted that the arm 33 is universally movable, by the mechanism described, about a point which lies upon the ideal axis of the arm. To compensate for changes of true air speed of the aircraft, which of course result in proportional variations of the component of air speed transverse to the line of fire of the gun, the effective length of arm 33 is variable by longitudinal adjustrnent of the aforementioned center of movement. The ratio between the transverse linear component of displacement of the center of ball 35 and the resulting angular deflection of arm 33 is thereby adjustable. Adjustment of the center ofmovement of arm 33 in the indicated manner is effected by moving the carriage 2i] longitudinally of the casing I. The position of the carriage bears a fixed relationship to the air speed, and air speed calibrations, generally designated 60, are provided along an upper edge of the casing, adapted to coact with an index mark 6| on the carriage. An adjustment knob 62 journaled in the side of the casing enables movement of the carriage, which is provided with a rack 63 upon its under side meshing with a pinion 64 fast upon the inner end of a shaft 65 to which the knob 62 is attached.

It will be noted that the operation of the mechanism is such that a line drawn through the ball socket assembly 31, 38 etc. in the direction of the line of flight and through the center of the. ball is maintained parallel to the line of flight by the movements of the ball socket engendered by elevational and training movements of the gun. In Figure 12 the point 0 represents the center of the ball, and point X represents the center of the sphere defined by the orbits which determine its movement; the line OX accordingly represents the component of own ships speed transverse to the axis of the gun bore. Y is the point about which universal movement of the yoke 22 occurs, and KY represents the projectile velocity component. OY represents the line of sight. The larger triangle having the termini of its hypotenuse at the gun breech and at the target, its adjacent side (V) constituting the extended gun bore axis and its opposite side (S) perpendicular to the last mentioned axis and extending through the target, is proportional to the smaller.

S OX (by similar triangles) It will be noted that by virtue of the indicated relationship, correction for changes of own ship's speed may be introduced by varying XY, which variation is effected by movement of the carriage 20 in the manner described above. This is of course much simpler mechanically than varying the diameter of the orbit sphere. The mechanically derived solution is actually a vector solution, the vectors comprising a bullet velocity vector along the gun bore axis and at own ship's speed vector along the line of flight. Under the most usual conditions, these vectors will lie in a slanted plane as indicated in Figure 13. In Figure 13 the relationship is indicated between the slant plane and a reference plane which includes the line of flight and a line perpendicular to-the line of flight, the perpendicular line being labeled Vertical in the figure. It will be seen that the total lateral deflection (TLD) and total vertical deflection (TVD) are measured in hori zontal and vertical planes, respectively, and that their vector sum determines the total deflection angle or lead angle, which lies in the slanted plane above referred to.

The sighting device I0 shown in Figures 1, 4, 7-, 9, and 10 may be of any suitable type, preferably collimating in character. Many such sights are known in the art, and the details of construction of the non-illuminated sight shown in the figures referred to form no part of the present invention and will not be considered.

In order to fix the sighting device in accurate.

- relation with respect to the gun, which is necesscribed so that it is either parallel to the axis of the gun or offset therefrom by any angle within the limits of the adjusting means serving to connect case I to pedestal 3. A pin 81 which accurately fits the holes 85, 86 is provided, preferably secured to the case as by the chain 88 and adapted to be removably held in the spring clip 89 when not in use. When the holes are aligned the pin may be projected thereinto in the mannershown in Figure 5. The pin thus serves both to determine that accurate alignment has been secured, and to lock the parts in the aligned relationship.

A novel illuminated sighting device especially suited for use in conjunction with my improved compensating structure is shown in Figures 14-17, inclusive. As there indicated, a pair of complementary prisms are provided, the lower of which, designated 10, is right-triangular in vertical cross section. The upper prism ll, of generally similar shape but provided with a curved upper surface, is cemented to the lower to pro:

vide a generally rectangular assembly so sitioned that the gunners line of sight extends through the inclined faces. The base of the prism assembly is supported in a skeletonized frame 14 and an opaque mask 15 extending across the bottom of the lower prism is perforated, as best shown in Figure 17 at 76 to provide a suit able reticle. The mask may be formed of paint and the reticle scratched therein. The reticle is illuminated from beneath by an incandescent bulb 11, the light being directed upwardly by a suitable reflector 78. The reflector is also of parabolic section and mounted rigidly upon the post IE to turn therewith. The lamp socket I9 is housed in an enlarged upper extremity of the post and the prism assembly turns about the vertical post axis with the post and the illuminating assembly, but is independently rockable about the transverse axis provided by the trunnion sight bearings II when actuated by the vertical deflector rod 24. One of the inclined mating prism surfaces is half silvered, as indicated at 80, so that the reticle image, divided. is projected both forwardly, by reflected light, in the line of sight, and upwardly, by transmitted light, to the curved upper surface of the top prism II. From the top mirror coating 82 the reticle image is projected downwardly upon the half silvered coating 80. The curvature of the top mirror 82 is such as to eliminate parallax and provide a collimating effect. A light-tight box 90 is formed by depending panels attached at their upper ends to the prism frame 74. The side panels 9| conform at their bottoms to the curvature of the reflector I8 and fit closely against the ends of the reflector, while the front and rear panels as 92 also terminate close to the reflector and may carry flexible wipers 93 bearing thereagainst to insure light-tight contact.

While it will be apparent that the preferred embodiment of my invention herein disclosed is well calculated adequately to fulfill the objects and advantages primarily stated, it will be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subjoined claims.

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. In a compensating gunsight for use in conjunction with a universally mounted gun, a sighting element universally movable with respect to.the gun to provide a lead angle which compnatesio tfi"'.. e Speed .fiiitfimounting ve means for moving the sighting eIement'including a planetary carrier having a hollow drive shaft, means for rotating said drive shaft in response to elevational movements of said gun, a planetary gear mounted on said planetary carrier with its plane of rotation normal to the orbit of said carrier and offset from the axis of rotation of said carrier, a driving gear for said planetary gear having a shaft extending through the hollow drive shaft for said carrier, means for rotating said driving gear in response to movement of the gun in train, a sight driver rotatablygnounted at one end a ball for insertion into said socket so that said ball is movable .over the surface of a hypothetical sphere of radius equal to the offset distance between said sight driver and the rotational axis of said planetary gear.

2. In a compensating gunsight for use in conjunction with a universally mounted gun, a sighting element universally movable with respect to the gun to provide a lead angle which compeneg pr the Speed .ortiieiisitffifitifiefiliis amafi forflmloving the sighting-element including a "planetary carrier having a hollow drive shaft, means for rotating said drive shaft in response to elevational movements of said gun, a planetary gear mounted on said planetary carrier with its plane of rotation normal to the orbit of said carrier and offset from the axis of rotation of said carrier, a driving gear for said planetary gear having a shaft extending through the hollow drive shaft for said carrier, means for rotating said driving gear in response to movement of the gun in train, a sight driver attached to said planetary gear at a point offset from the rotational axis of said planetary gear, said sight driver extending parallel to the rotational axis of said planetary gear and provided with a socket, a sight arm for moving said sighting element having at one end a ball for insertion into said socket so that said ball is movable over the surface of a hypothetical sphere of radius equal to the ofiset distance between said sight driver and the rotational axis of said planetary gear, said sighting element moving means including a parallel linkage mechanism, said sight arm forming a support for one side of said parallel linkage mechanism so that movement of the sight arm will be imparted to the sighting element,

adjustable'along said sight ,arm in, accordance with the speed of said mounting vehicle.

3. A compensating gunsight, as defined in claim 2, wherein a second side of said parallel linkage mechanism is pivotally mounted for rotational movement and fixed against movement lengthwise of itself, said one side and said sighting element being pivotally mounted at opposite ends of said second side.

EUGENE H. IRASEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Ser. No. 374,007, Allec (A. Apr. 27, 1943.

P. C.) published 

